can i add <?php ob_flush(); ?> <?php flush(); ?> in wordpress code?

I have read that it will save site load time of avarage 1.5 seconds so i want to use this code into my wordpress website , But i have no idea what these code does and how i can use this in wordpress website ? In which file i can use this code ?

<?php ob_flush(); ?>
<?php flush(); ?>

I am using wordpress can i use this code ? what this code does and how can i use this in wordpress ??

P.S : is this cache clearning code ? if yes then i am suing wp super cache should i need this code ??